IMPORTANCE OF LOWER
INSICOR POSITION IN
TREATMENT PLANING
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in cont...
INTRODUCTION
 For nearly two decades Dr Charles.H.
Tweed through his experience found out
that the axial inclination & po...
INCISOR POSTION AND
FACIAL ESTHETICS
 Aligning dentoalveolar segment alone does
not plays an important role in achieving
...
SOFT TISSUE PROFILE
 Thick upper & lower
lips extreme lip
protrusion with a
thin soft tissue
covering the chin
accentuate...
SOFT TISSUE PROFILE
 Average lip
protrusion and
average soft tissue
facial convexity.
www.indiandentalacademy.com
SOFT TISSUE PROFILE
 Retrusive lip that are
also thin in relation
to the thickness of
the soft tissue in the
chin area.
w...
SOFT TISSUE PROFILE
 Normal profile shows a facial convexity
(glabella-subnasale-soft tissue pogion) of
13 degree. Upper ...
www.indiandentalacademy.com
Tweed’s facial esthetics(1954)
 Charles.H.Tweed with
his clinical experience
found out a
cephalometric norms in
relation ...
Rickett’s lower incisor position
(1957)
 A-pog line used as
references line.
 In an average lower incisal
was located ap...
Bell, White & Profit norms
 Lower incisor to A-pog
- Angular measurement- 24+5
-Linear ,, -3mm(males)
1mm(females).
-L 1 ...
Burstone
 Lower incisor to mandibular plane
angle-95.9+5.2 degree.
www.indiandentalacademy.com
Down’s analysis
 Lower incisor to
mandibular plane-
91.7+4 degree.
www.indiandentalacademy.com
MCNAMARA ANALYSIS
 Mandibular lower
incisor to A-Pog
line-1-3mm.
www.indiandentalacademy.com
Steiner analysis
 Lower incisor to NB-
4mm & 25 degree.
www.indiandentalacademy.com
Rotation of Mandible and Incisor
Compensation
 Growth of jaws creates a space into
which the teeth erupts . The rotationa...
Rotation of Mandible and Incisor
Compensation
 Internal rotation of mandible.
 Upward & forward of mandible.
 Results i...
Incisor Compensation in Short
Face individuals
 Excessive rotation .
 Incisor tend to be
carried into
overlapping positi...
Incisor Compensation in Long
Face individuals
 Clockwise rotation
of mandible.
 Result in open bite
due to lack of over
...
Skeletal Discrepancy & Incisor
Compensation.
 Cephalo-caudal growth determines the rate of
growth of maxilla & mandible w...
Cl-III Situation
 Prognathic mandible
and retrognathic
maxilla, the upper
incisor lean labially
more than average and
lin...
Cl-III Situation
 Normal maxilla with
prognathic mandible,
the upper incisor
position and axial
inclination are normal
bu...
Cl-II Situation
 Prognathic maxilla
and retrognathic
mandible.
 Lower incisor are
flared and the upper
incisor are retru...
Cl-II Situation
 Normal maxilla and
retrognathic
mandible.
 The angulations and
position of the upper
incisor are normal...
Order of frequency of congenitally
missing teeth
 Maxillary & Mandibular 3rd molar.
 Maxillary lateral incisor.
 Mandib...
Lower extraction
 Extraction of teeth to resolve
crowding has been an accepted
treatment strategy for decades.
Non-extrac...
Indication for incisor extraction
(Albert Owen)
 Cl-I molar relationship.
 Moderately crowded lower incisor.
 In cases ...
Contd
 Witzel found that premolar extraction had less
tendency to become crowded then patient
treated non extraction. He ...
Contd
 Riedel has suggested that in patient with
severely crowed mandibular arches the
removal of 1 or more mandibular in...
Disadvantages of incisor extraction
 Disturbances in occlusion.
 Reopening of extraction spaces.
 Increased overjet.
 ...
Methods for eliminating over jet in
lower incisor extraction cases
 Extraction of upper 4s &lower incisor
result in good ...
Lower central incisor tip & torque
values of various PAE systems
 Andrews- 2/-1
 Roth- 2/-1
 Alexander- 0/-5
 Burstone...
Lower lateral incisor tip & torque
values of various PAE systems
 Andrews- 2/-1
 Roth- 2/-1
 Alexander- 0/-5
 Burstone...
Prevention of lower incisor
flaring during treatment
 Functional appliances
-Incisal capping
-Avoid acrylic contact on li...
Prevention of lower incisor
flaring during treatment
 Fixed appliances
-Avoid looped arch wires.
-Avoid long term use of ...
Lower incisor position
and stability
Raleigh williams(1986-JCO)
Six keys in eliminating lower retention
www.indiandentalac...
FIRST KEY
 The incisal edge of the lower incisor should be placed
on the A-P line or 1 mm in front of it. This is the
opt...
www.indiandentalacademy.com
Contd
 Appliance control is required to achieve optimal
position of the lower incisor consistently at the end of
treatmen...
Second key
 The lower incisor apices should be spread
distally to the crowns more than is generally
considered appropriat...
www.indiandentalacademy.com
Third key
 The apex of the lower cuspid should be
positioned distal to the crown.
 This angulation of the lower cuspid i...
www.indiandentalacademy.com
Fourth key
 All four lower incisor apices must be in the same labiolingual
plane . Spreading the apices of the lower inci...
Contd
 Experience has shown that the labiolingual apical
displacement of the lower incisors can occur easily if
round wir...
www.indiandentalacademy.com
Fifth key
 The lower cuspid root apex must be positioned
slightly buccal to the crown apex. This is extremely
important b...
Sixth key
 The lower incisors should be slenderized as needed after
treatment. Lower incisors that have sustained no prox...
www.indiandentalacademy.com
Contd
 The second source of hidden pressure
is an adverse tooth-jaw relationship.
 Flattening lower incisor contact poin...
Occlusal forces in stability of incisor
 Depending on the axial inclination and
position of the incisor different effects...
www.indiandentalacademy.com
Mandibular incisor school of thought
 Grieve &Tweed suggested that the
mandibular incisor must be kept upright
over basal...
BASIC THEOREM-6
 If the lower incisor are placed upright
over basal bone, they are more like to
remain in good alignment....
BASIC THEOREM-9
 Arch form ,particularly in the mandibular
arch, cannot be permantly altered by
appliance therapy. Theref...
Conclusion
 Modification of the facial profile by
orthodontic means depends on other
factors besides inclination of anter...
Thank you
For more details please visit
www.indiandentalacademy.com
www.indiandentalacademy.com
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Importance of liwer incisor position in treatment planning /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
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Importance of liwer incisor position in treatment planning /certified fixed orthodontic courses by Indian dental academy

  1. 1. IMPORTANCE OF LOWER INSICOR POSITION IN TREATMENT PLANING www.indiandentalacademy.com INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
  2. 2. INTRODUCTION  For nearly two decades Dr Charles.H. Tweed through his experience found out that the axial inclination & position of the mandibular incisor has been regarded as a factor of primary importance in the attainment of facial esthetics  But now over the years there has been a progression towards more precise definition of stability in incisor positioning based on 3 important factors - facial esthetics,lip protrusion & perioral function. www.indiandentalacademy.com
  3. 3. INCISOR POSTION AND FACIAL ESTHETICS  Aligning dentoalveolar segment alone does not plays an important role in achieving facial esthetics.  Dentoalveolar segment and soft tissue covering are the important factors in achieving facial esthetics.  Considering Ricketts concept in lower incisor position 3 clinical situations can taken into account www.indiandentalacademy.com
  4. 4. SOFT TISSUE PROFILE  Thick upper & lower lips extreme lip protrusion with a thin soft tissue covering the chin accentuates the lip protrusion. www.indiandentalacademy.com
  5. 5. SOFT TISSUE PROFILE  Average lip protrusion and average soft tissue facial convexity. www.indiandentalacademy.com
  6. 6. SOFT TISSUE PROFILE  Retrusive lip that are also thin in relation to the thickness of the soft tissue in the chin area. www.indiandentalacademy.com
  7. 7. SOFT TISSUE PROFILE  Normal profile shows a facial convexity (glabella-subnasale-soft tissue pogion) of 13 degree. Upper & lower lip protrusion is measured in relation in relation to the subnasale-pogion line, which offers the advantage of not being directly associated with the nose. The upper lip protrudes 3.5mm and the lower lip protrudes 3.0mm. This measurement of lip protrusion remains relatively stable , reduces only slightly with the age. www.indiandentalacademy.com
  8. 8. www.indiandentalacademy.com
  9. 9. Tweed’s facial esthetics(1954)  Charles.H.Tweed with his clinical experience found out a cephalometric norms in relation to lower incisor angulation in relation to -FMA-25 degree. -FMIA-65 degree. -IMPA-90 degree. www.indiandentalacademy.com
  10. 10. Rickett’s lower incisor position (1957)  A-pog line used as references line.  In an average lower incisal was located approximately 0.5mm anterior to the reference line.  Angular measurement-a line through the long axis of the lower to the A-pog plane- incisor inclined at an average of 20.5 degree.  E-plane-upper lip 1.0mm posterior , lower lip 0.3mm ahead. www.indiandentalacademy.com
  11. 11. Bell, White & Profit norms  Lower incisor to A-pog - Angular measurement- 24+5 -Linear ,, -3mm(males) 1mm(females). -L 1 to Mandibular plane angle-95+7 degree. www.indiandentalacademy.com
  12. 12. Burstone  Lower incisor to mandibular plane angle-95.9+5.2 degree. www.indiandentalacademy.com
  13. 13. Down’s analysis  Lower incisor to mandibular plane- 91.7+4 degree. www.indiandentalacademy.com
  14. 14. MCNAMARA ANALYSIS  Mandibular lower incisor to A-Pog line-1-3mm. www.indiandentalacademy.com
  15. 15. Steiner analysis  Lower incisor to NB- 4mm & 25 degree. www.indiandentalacademy.com
  16. 16. Rotation of Mandible and Incisor Compensation  Growth of jaws creates a space into which the teeth erupts . The rotational pattern of jaw growth obviously influences the magnitude of tooth eruption. It can also influences the direction of eruption and the ultimate anterior-posterior of the incisor teeth. www.indiandentalacademy.com
  17. 17. Rotation of Mandible and Incisor Compensation  Internal rotation of mandible.  Upward & forward of mandible.  Results in eruption of incisor posteriorly.  Molar migrates mesially.  Decreases in arch length. www.indiandentalacademy.com
  18. 18. Incisor Compensation in Short Face individuals  Excessive rotation .  Incisor tend to be carried into overlapping position.  Results in deep bite.  Displacing them lingually results in crowding. www.indiandentalacademy.com
  19. 19. Incisor Compensation in Long Face individuals  Clockwise rotation of mandible.  Result in open bite due to lack of over eruption in incisor region.  Proclination of incisors. www.indiandentalacademy.com
  20. 20. Skeletal Discrepancy & Incisor Compensation.  Cephalo-caudal growth determines the rate of growth of maxilla & mandible which normally leads to Cl-I skeletal relationship where maxilla stops its growth earlier than mandible and controls the mandibular growth by safety value mechanism and accordingly the dentition undergoes a stable adaptation. In a situation where maxilla & mandible is altered and not in concurrent with each other which can lead to clinical situation like Cl-III,Cl-II for this condition the anterior segment arch undergoes compensation. www.indiandentalacademy.com
  21. 21. Cl-III Situation  Prognathic mandible and retrognathic maxilla, the upper incisor lean labially more than average and lingual inclination of the lower incisor for compensation of prognathic denture base relationship. www.indiandentalacademy.com
  22. 22. Cl-III Situation  Normal maxilla with prognathic mandible, the upper incisor position and axial inclination are normal but the lower incisor usually lean lingually for compensation of prognathic denture base relationship( tight lower lip will tend to retruded the lower in lingual). www.indiandentalacademy.com
  23. 23. Cl-II Situation  Prognathic maxilla and retrognathic mandible.  Lower incisor are flared and the upper incisor are retruded ,this dental compensation result in proclination of normal over jet. www.indiandentalacademy.com
  24. 24. Cl-II Situation  Normal maxilla and retrognathic mandible.  The angulations and position of the upper incisor are normal but the lower incisor are proclined labially to establish normal over jet. www.indiandentalacademy.com
  25. 25. Order of frequency of congenitally missing teeth  Maxillary & Mandibular 3rd molar.  Maxillary lateral incisor.  Mandibular 2rd premolar.  Mandibular incisor.  Maxillary second premolar. www.indiandentalacademy.com
  26. 26. Lower extraction  Extraction of teeth to resolve crowding has been an accepted treatment strategy for decades. Non-extraction therapy in crowded cases is usually thought to lead to post retention relapse. www.indiandentalacademy.com
  27. 27. Indication for incisor extraction (Albert Owen)  Cl-I molar relationship.  Moderately crowded lower incisor.  In cases of bone loss, periodontitis & fracture.  Mild or no crowding in upper arch.  Acceptable soft tissue profile.  Minimal to moderate over bite & over jet.  Minimal growth potential.  Missing lateral incisor or peg laterals.  Mandibular tooth material excess. www.indiandentalacademy.com
  28. 28. Contd  Witzel found that premolar extraction had less tendency to become crowded then patient treated non extraction. He found no signifant corelation between pretreatment and post retention incisor alignment and no significant corelation between stability and changes in mandibular incisor changes in mandibular position or angulation.  Kokich and Shapiro believe that in case selection for intentional extraction of mandibular incisor can simplify orthodontic mechanics and enhances both theocclusal and cosmetic results of treatment. www.indiandentalacademy.com
  29. 29. Contd  Riedel has suggested that in patient with severely crowed mandibular arches the removal of 1 or more mandibular incisor is only the logical alternative which may allow for increased stability of the mandibular stability of the mandibular anteriors without retention and in mainting arch form without expansion of inter canine width when compared with non extraction and premolar extraction. www.indiandentalacademy.com
  30. 30. Disadvantages of incisor extraction  Disturbances in occlusion.  Reopening of extraction spaces.  Increased overjet.  Increased overbite. www.indiandentalacademy.com
  31. 31. Methods for eliminating over jet in lower incisor extraction cases  Extraction of upper 4s &lower incisor result in good occlusion.  In case of unilateral extraction of incisor the molar on the affected side will be in Cl-I or Cl-III relationship.  In case of unilateral missing incisor it is advisable to avoid extraction in that quadrant and use canine as an incisor. www.indiandentalacademy.com
  32. 32. Lower central incisor tip & torque values of various PAE systems  Andrews- 2/-1  Roth- 2/-1  Alexander- 0/-5  Burstone- 0/-1  Hilgers- 0/-1  Ricketts- 0/0  Bench- 2/-1  Level anchorage- 2/0  Hasund - 0/0  Cetlin- 0/0  Orthos - 2/-5  MBT- 0/-6 www.indiandentalacademy.com
  33. 33. Lower lateral incisor tip & torque values of various PAE systems  Andrews- 2/-1  Roth- 2/-1  Alexander- 0/-5  Burstone- 0/-1  Hilgers- 0/-1  Ricketts- 0/0  Bench- 2/-1  Level anchorage- 2/0  Hasund - 0/0  Cetlin- 0/0  Orthos - 4/-5  MBT- 0/-6 www.indiandentalacademy.com
  34. 34. Prevention of lower incisor flaring during treatment  Functional appliances -Incisal capping -Avoid acrylic contact on lingual surface of lower incisor.  With fixed appliance. -Torque incorporated arch wires. -5 degree torque. -filling the slot by full size arch wire. www.indiandentalacademy.com
  35. 35. Prevention of lower incisor flaring during treatment  Fixed appliances -Avoid looped arch wires. -Avoid long term use of Niti,Cu niti. -Reverse torqueing auxillaries. -Lace back. -Cinch back of arch wires. -Rectangular arch wire. -Segmental mechanics. -Filling the slot by full size arch wire. www.indiandentalacademy.com
  36. 36. Lower incisor position and stability Raleigh williams(1986-JCO) Six keys in eliminating lower retention www.indiandentalacademy.com
  37. 37. FIRST KEY  The incisal edge of the lower incisor should be placed on the A-P line or 1 mm in front of it. This is the optimum position for lower incisor stability .It also creates optimum balance of soft tissues in the lower third of the face for all the variations in apical base differences within the normal range.  The angulation of lower incisors has not proven to be relevant to their stability. A lower incisor angulation of 90° to the mandibular plane, or 65° to the Frankfort plane, may be esthetically appropriate and stable for those who have optimal Northern European skeletal configurations, but not for members of other ethnic groups. www.indiandentalacademy.com
  38. 38. www.indiandentalacademy.com
  39. 39. Contd  Appliance control is required to achieve optimal position of the lower incisor consistently at the end of treatment. Point A on the upper end of the A-P line can be retracted. Point P, at the lower end, will move forward or not depending on mandibular growth. With experience, the clinician will know how each end of this line changes, which procedures will place the lower incisor 1 mm in front of the line, whether extractions are necessary, and which teeth should be extracted.  If the lower incisor is advanced too far beyond the A-P line, relapse and crowding will occur. Lower incisors that are overly proclined in treatment— beyond one standard deviation— can only be maintained in such an untenable position with a fixed retainer. When the retainer is removed, the incisors will move lingually and become crowded. www.indiandentalacademy.com
  40. 40. Second key  The lower incisor apices should be spread distally to the crowns more than is generally considered appropriate and the apices of the lower lateral incisors must be spread more than those of the central incisors. The Begg technique is geared to achieve the necessary progressive spreading, but none of the current straightwire systems provides adequate lower incisor slot angulations to bring about sufficient progressive spreading of lower incisor apices. When the lower incisor roots are left convergent, or even parallel, the crowns tend to bunch up and a fixed lower retainer is usually needed to prevent post-treatment relapse. www.indiandentalacademy.com
  41. 41. www.indiandentalacademy.com
  42. 42. Third key  The apex of the lower cuspid should be positioned distal to the crown.  This angulation of the lower cuspid is important in creating post-treatment incisor stability because it reduces the tendency of the cuspid crown to tip forward into the incisor area. If this happens, the lower incisors crowd up, even if their roots are spread and the incisal edges are on the A-P line or 1mm in front of it. Distal inclination of the lower cuspid should be a standard treatment objective and is easily accomplished with the Begg or any straightwire technique. www.indiandentalacademy.com
  43. 43. www.indiandentalacademy.com
  44. 44. Fourth key  All four lower incisor apices must be in the same labiolingual plane . Spreading the apices of the lower incisor roots distally causes a strong reciprocal tendency for the crowns to move mesially. Moreover, as the roots are spread, the contact areas between the incisor crowns move upward toward the anatomical contact points, which are small, rounded, and near the incisal edge. Because of the strong mesial pressure on the crowns during the root spreading process, there is a tendency for these contact points to displace each other labiolingually. This results in a reverse movement of the apices linguolabially.  The displacement forces are considerably augmented by the increasing width of the lower incisor crown toward the incisal edge and contact point. This means that provision for the additional space must be made during the spreading process. Otherwise, labiolingual apical displacement of the lower incisors will tend to occur, and the degree to which it occurs will affect lower incisor posttreatment stability. www.indiandentalacademy.com
  45. 45. Contd  Experience has shown that the labiolingual apical displacement of the lower incisors can occur easily if round wires are used during the spreading process. To maintain labiolingual apical control during the spreading process— using uprighting springs in the third stage of Begg treatment— an edgewise sectional auxiliary in the incisor region along with the main round archwire is effective. With the edgewise technique, spreading begins at the start of treatment, so any labiolingual apical displacements occurring from the initial use of round wires can be corrected later when rectangular arches are used. www.indiandentalacademy.com
  46. 46. www.indiandentalacademy.com
  47. 47. Fifth key  The lower cuspid root apex must be positioned slightly buccal to the crown apex. This is extremely important because of its influence on post-treatment stability. All sorts of occlusal forces await their chance to exert lingual pressure on the lower cuspid crown. If the apex of the lower cuspid is lingual to the crown at the end of treatment, the forces of occlusion can more easily move the crown lingually toward the space reserved for the lower incisors because of these functional pressures plus a natural tendency for the crown to upright over its root apex. Even if a lower cuspid with abnormal lingual position of the apex were supported for many years with a fixed retainer, the crown would eventually move lingually when the restraint was removed. www.indiandentalacademy.com
  48. 48. Sixth key  The lower incisors should be slenderized as needed after treatment. Lower incisors that have sustained no proximal wear have round, small contact points, which are accentuated if the apices have been spread for stability . Consequently, the slightest amount of continuous mesial pressure can cause various degrees of collapse in the lower incisor segment.  There are two sources for post-treatment pressure on the lower incisors that may bring about a shifting or collapse even though all other key treatment requirements have been accomplished. One source is the molars. Current evidence indicates that natural mesial pressure is limited to the upper and lower molars. Molar pressure can cause displacement of lower incisor contact points. Removal of third molars does not eliminate the mesial pressure derived from the first and second molars, and "there is little rationale, based on present evidence, for the extraction of third molars solely to minimize present or future crowding of lower anterior teeth". www.indiandentalacademy.com
  49. 49. www.indiandentalacademy.com
  50. 50. Contd  The second source of hidden pressure is an adverse tooth-jaw relationship.  Flattening lower incisor contact points by slenderizing or stripping creates flat contact surfaces that help resist labiolingual crown displacement. This treatment also helps eliminate the need for lower incisor retention . www.indiandentalacademy.com
  51. 51. Occlusal forces in stability of incisor  Depending on the axial inclination and position of the incisor different effects are produced. -incisal force through the centre of resistance -lingual force anteriorly to the incisor. -lingually directed biting forces passes superior to the centre of resistance. www.indiandentalacademy.com
  52. 52. www.indiandentalacademy.com
  53. 53. Mandibular incisor school of thought  Grieve &Tweed suggested that the mandibular incisor must be kept upright over basal bone. www.indiandentalacademy.com
  54. 54. BASIC THEOREM-6  If the lower incisor are placed upright over basal bone, they are more like to remain in good alignment.  Attention should be directed to the proper angulation and placement of the mandibular segment. www.indiandentalacademy.com
  55. 55. BASIC THEOREM-9  Arch form ,particularly in the mandibular arch, cannot be permantly altered by appliance therapy. Therefore treatment should be directed towards maintaing the arch form presented by the malocclusion as much as possible. www.indiandentalacademy.com
  56. 56. Conclusion  Modification of the facial profile by orthodontic means depends on other factors besides inclination of anterior teeth, diagnostic criteria based solely on this factor are likely to be unreliable. www.indiandentalacademy.com
  57. 57. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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